Re: [PATCH v8 3/4] tee: optee: support tracking system threads

From: Sumit Garg
Date: Thu May 18 2023 - 02:26:16 EST

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In reply to: Etienne Carriere: "[PATCH v8 3/4] tee: optee: support tracking system threads"
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On Tue, 16 May 2023 at 18:24, Etienne Carriere
<etienne.carriere@xxxxxxxxxx> wrote:
>
> Adds support in the OP-TEE driver to keep track of reserved system
> threads. The optee_cq_*() functions are updated to handle this if
> enabled. The SMC ABI part of the driver enables this tracking, but the
> FF-A ABI part does not.
>
> The call queue list optee_call_queue::waiters is replaced by 2 lists,
> one for regular sessions and one system sessions. The struct also
> stores count of TEE thread contexts provisioned/used/reserved to
> track use of TEE resources. The logic allows at most 1 OP-TEE entry
> can be reserved to TEE system sessions. For sake of simplicity,
> initialization of call queue management is factorized into new
> helper function optee_cq_init().
>
> Co-developed-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> Signed-off-by: Etienne Carriere <etienne.carriere@xxxxxxxxxx>
> ---
> Changes since v7:
> - Changes the logic to reserve at most 1 call entry for system sessions
> as per patches v6 and v7 discussion threads (the 2 below bullets)
> and updates commit message accordingly.
> - Field optee_call_queue::res_sys_thread_count is replaced with 2 fields:
> sys_thread_req_count and boolean sys_thread_in_use.
> - Field optee_call_waiter::sys_thread is replaced with 2 fields:
> sys_thread_req and sys_thread_used.
> - Adds inline description comments for struct optee_call_queue and
> struct optee_call_waiter.
>

The implementation looks complex to me, see a simplified version [1]
of this patch.

[1] https://lists.trustedfirmware.org/archives/list/op-tee@xxxxxxxxxxxxxxxxxxxxxxxxx/thread/O4T3LI37GVBPW4MMVFLSM4EKTLHJNEJE/

-Sumit

> Changes since v6:
> - Moved out changes related to adding boolean system thread attribute
> into optee driver call queue and SMC/FF-A ABIs API functions. These
> changes were squashed into patch 1/4 of this patch v7 series.
> - Comment about adding a specific commit for call queue refactoring
> was not addressed such a patch would only introduce function
> optee_cq_init() with very little content in (mutex & list init).
> - Added Co-developed-by tag for Jens contribution as he's not responsible
> for the changes I made in this patch v7.
>
> No change since v5
>
> Changes since v4:
> - New change that supersedes implementation proposed in PATCH v4
> (tee: system invocation"). Thanks to Jens implementation we don't need
> the new OP-TEE services that my previous patch versions introduced to
> monitor system threads entry. Now, Linux optee SMC ABI driver gets TEE
> provisioned thread contexts count once and monitors thread entries in
> OP-TEE on that basis and the system thread capability of the related
> tee session. By the way, I dropped the WARN_ONCE() call I suggested
> on tee thread exhaustion as it does not provides useful information.
> ---
> drivers/tee/optee/call.c | 131 ++++++++++++++++++++++++++++--
> drivers/tee/optee/ffa_abi.c | 3 +-
> drivers/tee/optee/optee_private.h | 30 ++++++-
> drivers/tee/optee/smc_abi.c | 16 +++-
> 4 files changed, 167 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c
> index 152ae9bb1785..7aec64f0f7e0 100644
> --- a/drivers/tee/optee/call.c
> +++ b/drivers/tee/optee/call.c
> @@ -39,9 +39,28 @@ struct optee_shm_arg_entry {
> DECLARE_BITMAP(map, MAX_ARG_COUNT_PER_ENTRY);
> };
>
> +void optee_cq_init(struct optee_call_queue *cq, int thread_count)
> +{
> + mutex_init(&cq->mutex);
> + INIT_LIST_HEAD(&cq->normal_waiters);
> + INIT_LIST_HEAD(&cq->sys_waiters);
> + /*
> + * If cq->total_thread_count is 0 then we're not trying to keep
> + * track of how many free threads we have, instead we're relying on
> + * the secure world to tell us when we're out of thread and have to
> + * wait for another thread to become available.
> + */
> + cq->total_thread_count = thread_count;
> + cq->free_normal_thread_count = thread_count;
> +}
> +
> void optee_cq_wait_init(struct optee_call_queue *cq,
> struct optee_call_waiter *w, bool sys_thread)
> {
> + bool need_wait = false;
> +
> + memset(w, 0, sizeof(*w));
> +
> /*
> * We're preparing to make a call to secure world. In case we can't
> * allocate a thread in secure world we'll end up waiting in
> @@ -53,15 +72,46 @@ void optee_cq_wait_init(struct optee_call_queue *cq,
> mutex_lock(&cq->mutex);
>
> /*
> - * We add ourselves to the queue, but we don't wait. This
> - * guarantees that we don't lose a completion if secure world
> - * returns busy and another thread just exited and try to complete
> - * someone.
> + * We add ourselves to a queue, but we don't wait. This guarantees
> + * that we don't lose a completion if secure world returns busy and
> + * another thread just exited and try to complete someone.
> */
> init_completion(&w->c);
> - list_add_tail(&w->list_node, &cq->waiters);
> + w->sys_thread_req = sys_thread;
> + if (sys_thread) {
> + list_add_tail(&w->list_node, &cq->sys_waiters);
> + if (cq->sys_thread_in_use) {
> + need_wait = true;
> + } else {
> + cq->sys_thread_in_use = true;
> + w->sys_thread_used = true;
> + }
> + } else {
> + list_add_tail(&w->list_node, &cq->normal_waiters);
> + if (cq->total_thread_count) {
> + /*
> + * Claim a normal thread if one is available, else
> + * we'll need to wait for a normal thread to be
> + * released.
> + */
> + if (cq->free_normal_thread_count > 0)
> + cq->free_normal_thread_count--;
> + else
> + need_wait = true;
> + }
> + }
>
> mutex_unlock(&cq->mutex);
> +
> + while (need_wait) {
> + optee_cq_wait_for_completion(cq, w);
> + mutex_lock(&cq->mutex);
> + if (cq->free_normal_thread_count > 0) {
> + cq->free_normal_thread_count--;
> + need_wait = false;
> + }
> + mutex_unlock(&cq->mutex);
> + }
> }
>
> void optee_cq_wait_for_completion(struct optee_call_queue *cq,
> @@ -74,7 +124,10 @@ void optee_cq_wait_for_completion(struct optee_call_queue *cq,
> /* Move to end of list to get out of the way for other waiters */
> list_del(&w->list_node);
> reinit_completion(&w->c);
> - list_add_tail(&w->list_node, &cq->waiters);
> + if (w->sys_thread_req)
> + list_add_tail(&w->list_node, &cq->sys_waiters);
> + else
> + list_add_tail(&w->list_node, &cq->normal_waiters);
>
> mutex_unlock(&cq->mutex);
> }
> @@ -83,10 +136,19 @@ static void optee_cq_complete_one(struct optee_call_queue *cq)
> {
> struct optee_call_waiter *w;
>
> - list_for_each_entry(w, &cq->waiters, list_node) {
> + list_for_each_entry(w, &cq->sys_waiters, list_node) {
> if (!completion_done(&w->c)) {
> complete(&w->c);
> - break;
> + return;
> + }
> + }
> +
> + if (!cq->total_thread_count || cq->free_normal_thread_count > 0) {
> + list_for_each_entry(w, &cq->normal_waiters, list_node) {
> + if (!completion_done(&w->c)) {
> + complete(&w->c);
> + break;
> + }
> }
> }
> }
> @@ -104,6 +166,11 @@ void optee_cq_wait_final(struct optee_call_queue *cq,
> /* Get out of the list */
> list_del(&w->list_node);
>
> + if (w->sys_thread_used)
> + cq->sys_thread_in_use = false;
> + else
> + cq->free_normal_thread_count++; /* Release a normal thread */
> +
> /* Wake up one eventual waiting task */
> optee_cq_complete_one(cq);
>
> @@ -119,6 +186,31 @@ void optee_cq_wait_final(struct optee_call_queue *cq,
> mutex_unlock(&cq->mutex);
> }
>
> +bool optee_cq_inc_sys_thread_count(struct optee_call_queue *cq)
> +{
> + if (cq->total_thread_count <= 1)
> + return false;
> +
> + mutex_lock(&cq->mutex);
> + if (!cq->sys_thread_req_count)
> + cq->free_normal_thread_count--;
> + cq->sys_thread_req_count++;
> + mutex_unlock(&cq->mutex);
> +
> + return true;
> +}
> +
> +void optee_cq_dec_sys_thread_count(struct optee_call_queue *cq)
> +{
> + mutex_lock(&cq->mutex);
> + cq->sys_thread_req_count--;
> + if (!cq->sys_thread_req_count)
> + cq->free_normal_thread_count++;
> + /* If there's someone waiting, let it resume */
> + optee_cq_complete_one(cq);
> + mutex_unlock(&cq->mutex);
> +}
> +
> /* Requires the filpstate mutex to be held */
> static struct optee_session *find_session(struct optee_context_data *ctxdata,
> u32 session_id)
> @@ -361,6 +453,27 @@ int optee_open_session(struct tee_context *ctx,
> return rc;
> }
>
> +int optee_system_session(struct tee_context *ctx, u32 session)
> +{
> + struct optee_context_data *ctxdata = ctx->data;
> + struct optee *optee = tee_get_drvdata(ctx->teedev);
> + struct optee_session *sess;
> + int rc = -EINVAL;
> +
> + mutex_lock(&ctxdata->mutex);
> +
> + sess = find_session(ctxdata, session);
> + if (sess && !sess->use_sys_thread &&
> + optee_cq_inc_sys_thread_count(&optee->call_queue)) {
> + rc = 0;
> + sess->use_sys_thread = true;
> + }
> +
> + mutex_unlock(&ctxdata->mutex);
> +
> + return rc;
> +}
> +
> int optee_close_session_helper(struct tee_context *ctx, u32 session,
> bool system_thread)
> {
> @@ -378,6 +491,8 @@ int optee_close_session_helper(struct tee_context *ctx, u32 session,
> msg_arg->session = session;
> optee->ops->do_call_with_arg(ctx, shm, offs, system_thread);
>
> + if (system_thread)
> + optee_cq_dec_sys_thread_count(&optee->call_queue);
> optee_free_msg_arg(ctx, entry, offs);
>
> return 0;
> diff --git a/drivers/tee/optee/ffa_abi.c b/drivers/tee/optee/ffa_abi.c
> index 5fde9d4100e3..0c9055691343 100644
> --- a/drivers/tee/optee/ffa_abi.c
> +++ b/drivers/tee/optee/ffa_abi.c
> @@ -852,8 +852,7 @@ static int optee_ffa_probe(struct ffa_device *ffa_dev)
> if (rc)
> goto err_unreg_supp_teedev;
> mutex_init(&optee->ffa.mutex);
> - mutex_init(&optee->call_queue.mutex);
> - INIT_LIST_HEAD(&optee->call_queue.waiters);
> + optee_cq_init(&optee->call_queue, 0);
> optee_supp_init(&optee->supp);
> optee_shm_arg_cache_init(optee, arg_cache_flags);
> ffa_dev_set_drvdata(ffa_dev, optee);
> diff --git a/drivers/tee/optee/optee_private.h b/drivers/tee/optee/optee_private.h
> index b68273051454..b8f22d7b34a6 100644
> --- a/drivers/tee/optee/optee_private.h
> +++ b/drivers/tee/optee/optee_private.h
> @@ -40,15 +40,39 @@ typedef void (optee_invoke_fn)(unsigned long, unsigned long, unsigned long,
> unsigned long, unsigned long,
> struct arm_smccc_res *);
>
> +/*
> + * struct optee_call_waiter - TEE entry may need to wait for a free TEE thread
> + * @list_node Reference in waiters list
> + * @c Waiting completion reference
> + * @sys_thread_req True only if waiter belongs to a requested system thread
> + * @sys_thread_used True only if waiter is consuming the system thread
> + */
> struct optee_call_waiter {
> struct list_head list_node;
> struct completion c;
> + bool sys_thread_req;
> + bool sys_thread_used;
> };
>
> +/*
> + * struct optee_call_queue - OP-TEE call queue management
> + * @mutex Serializes access to this struct
> + * @normal_waiters List of normal threads waiting to enter OP-TEE
> + * @sys_waiters List of system threads waiting to enter OP-TEE
> + * @total_thread_count Overall number of thread context in OP-TEE or 0
> + * @free_normal_thread_count Number of normal threads context free in OP-TEE
> + * @sys_thread_req_count Number of registered system thread requests
> + * @sys_thread_in_use True only if reserved system entry is consumed
> + */
> struct optee_call_queue {
> /* Serializes access to this struct */
> struct mutex mutex;
> - struct list_head waiters;
> + struct list_head normal_waiters;
> + struct list_head sys_waiters;
> + int total_thread_count;
> + int free_normal_thread_count;
> + int sys_thread_req_count;
> + bool sys_thread_in_use;
> };
>
> struct optee_notif {
> @@ -254,6 +278,7 @@ int optee_supp_send(struct tee_context *ctx, u32 ret, u32 num_params,
> int optee_open_session(struct tee_context *ctx,
> struct tee_ioctl_open_session_arg *arg,
> struct tee_param *param);
> +int optee_system_session(struct tee_context *ctx, u32 session);
> int optee_close_session_helper(struct tee_context *ctx, u32 session,
> bool system_thread);
> int optee_close_session(struct tee_context *ctx, u32 session);
> @@ -303,6 +328,9 @@ static inline void optee_to_msg_param_value(struct optee_msg_param *mp,
> mp->u.value.c = p->u.value.c;
> }
>
> +void optee_cq_init(struct optee_call_queue *cq, int thread_count);
> +bool optee_cq_inc_sys_thread_count(struct optee_call_queue *cq);
> +void optee_cq_dec_sys_thread_count(struct optee_call_queue *cq);
> void optee_cq_wait_init(struct optee_call_queue *cq,
> struct optee_call_waiter *w, bool sys_thread);
> void optee_cq_wait_for_completion(struct optee_call_queue *cq,
> diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
> index e2763cdcf111..3314ffeb91c8 100644
> --- a/drivers/tee/optee/smc_abi.c
> +++ b/drivers/tee/optee/smc_abi.c
> @@ -1209,6 +1209,7 @@ static const struct tee_driver_ops optee_clnt_ops = {
> .release = optee_release,
> .open_session = optee_open_session,
> .close_session = optee_close_session,
> + .system_session = optee_system_session,
> .invoke_func = optee_invoke_func,
> .cancel_req = optee_cancel_req,
> .shm_register = optee_shm_register,
> @@ -1356,6 +1357,16 @@ static bool optee_msg_exchange_capabilities(optee_invoke_fn *invoke_fn,
> return true;
> }
>
> +static unsigned int optee_msg_get_thread_count(optee_invoke_fn *invoke_fn)
> +{
> + struct arm_smccc_res res;
> +
> + invoke_fn(OPTEE_SMC_GET_THREAD_COUNT, 0, 0, 0, 0, 0, 0, 0, &res);
> + if (res.a0)
> + return 0;
> + return res.a1;
> +}
> +
> static struct tee_shm_pool *
> optee_config_shm_memremap(optee_invoke_fn *invoke_fn, void **memremaped_shm)
> {
> @@ -1609,6 +1620,7 @@ static int optee_probe(struct platform_device *pdev)
> struct optee *optee = NULL;
> void *memremaped_shm = NULL;
> unsigned int rpc_param_count;
> + unsigned int thread_count;
> struct tee_device *teedev;
> struct tee_context *ctx;
> u32 max_notif_value;
> @@ -1636,6 +1648,7 @@ static int optee_probe(struct platform_device *pdev)
> return -EINVAL;
> }
>
> + thread_count = optee_msg_get_thread_count(invoke_fn);
> if (!optee_msg_exchange_capabilities(invoke_fn, &sec_caps,
> &max_notif_value,
> &rpc_param_count)) {
> @@ -1725,8 +1738,7 @@ static int optee_probe(struct platform_device *pdev)
> if (rc)
> goto err_unreg_supp_teedev;
>
> - mutex_init(&optee->call_queue.mutex);
> - INIT_LIST_HEAD(&optee->call_queue.waiters);
> + optee_cq_init(&optee->call_queue, thread_count);
> optee_supp_init(&optee->supp);
> optee->smc.memremaped_shm = memremaped_shm;
> optee->pool = pool;
> --
> 2.25.1
>

Next message: Marion & Christophe JAILLET: "Re: [PATCH 1/3] drm/amd/display: drop redundant memset() in get_available_dsc_slices()"
Previous message: Claudiu Beznea: "[PATCH] ARM: at91: pm: fix imbalanced reference counter for ethernet devices"
In reply to: Etienne Carriere: "[PATCH v8 3/4] tee: optee: support tracking system threads"
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